_____________________________________________________________ I have been asked many times to help explain why we have so many things that can affect the run quality of Stunt engines. I will touch on a few of them , and hopefully help to eliminate some of these problems . Among them are tanks and fuel systems, glo plugs , fuel ,and overheating What are things that make for a great, or bad engine run. We see these things most every weekend, and it is a very big point of frustration to many modelers. We all want our engines to run right, and it is nice when it goes through the pattern smoothly, coming on and off, exactly when and where you want it. Unfortunately, a lot of times, they growl , belch, shut off ,seem to have a mind of their own ,and are a total pain to deal with. One of the biggest causes of this that I have seen is improper fuel. Fuel is one of the most critical aspects in running model motors. Use the right fuel and you will probably notice nothing; the wrong fuel will have you grumbling, or worse, will have your motor screaming, belching and running with absolutely no consistency whatsoever.

Most fuels on the market today use a synthetic base and are blended for the R/C sport flier. These are typically very low on oil content, usually in the 12% through 15% range. This is never acceptable for our use in C/L Stunt. There are many reasons but the most important is the fact that we normally do not run our engines in a peaked two cycle, but rather a broad range of four cycle and rich two cycling. Any time you run with the motor set to come on and off in the maneuvers (like a typical 4-2 break) you are not only asking the fuel to lubricate the motor, it also has to cool the engine. The only way you can run in a 4-2 is to heat and cool the parts in the combustion chamber very rapidly. This makes the oil content critical, because it’s the unburned oil that helps carry away the heat.

Years ago, most fuels had only one oil ,castor. This is still a very good oil with many good but some bad points. Some of its good points; it carries heat out of the motor and gives a good plating action on all surfaces, especially when they’re hot. It also has tendencies to move toward hot surfaces, helping to protect them. A few of its bad points; it burns and sticks to the piston sides and the ring groove and all other parts that are hot enough, and will carbonize the chamber. It will stick rings in their grooves, freeze wrist pins and build up ridges on sleeves. This causes excess friction and heat and will ruin your motor in time.

The alternative to castor is synthetic oil and almost all fuels have these in them; the vast majority has all synthetic. Virtually all fuel manufactures use one type of synthetic; these are normally polyalkylene glycol based oils. They are mostly made up of alcohol started linear polymers , of oxypropylene groups. These are made by several companies and are available in a large range of molecular weights and viscosities.

This group of oils is the modern version of the old Ucon oils and also have good and bad points. Some of the goods points; they are very good lubes without containing any wax; they have outstanding load carrying capacity, film strength, anti-wear properties, are resistant to sludge formation, and will help keep your engine clean. The bad points are they give no rust protection by themselves, they don’t plate hot surfaces as well as castor and they burn at high heats.

As you can see, both oils have advantages and disadvantages to them; it’s for these reasons that they work much better blending together than they could ever work alone. Throughout many years of flying ,testing and other research have proven this to me beyond any doubt; plus you can see this for yourself. Recently, a friend of mine had a motor that would go into the pattern and lean out and act very inconsistently. The only change that was made was to substitute one tank of my fuel in the model. The results were drastically different; the motor now ran very smoothly, going into a two cycle instantly when the nose was raised and back into a four cycle instantly when the plane was leveled. This was tried back and forth both fuels; his and mine. The results were the same every time. I see this type of thing happen much too often, and it is extremely frustrating for Flyers to deal with. They often blame these fuel problems on cooling, cowlings, motors ,fuel filters, and unfortunately some don’t have a clue how to recognize or solve this problem. This is a frustration that you can live without!

I would like to tell you there is one Stunt fuel formula to run in all motors, I said I would like to tell you that…unfortunately this is not the case, and will never be as long as we have such a wide range of motors and running styles. What I will tell you is a good formula for the most common types of engines. Make sure you pick a fuel supplier who will give you consistent fuel day to day ,and will blend fuel for your motor needs or has fuel to match your needs. Stay away from any supplier who will not tell you the oil percentage, or who say one type works for all motors. I see this much to often also, It is unfortunate, but a lot of fuel manufactures will try to fool you about the oil and nitro percentage. One trick is to measure by weight and not volume. Doing so, they can claim that the fuel is for example 18 % oil , when in reality it is only 14.9 % oil content. Using weight for ingredient , they can put in a lot less oil and nitro . Other things are changing oil types, going to cheaper Nitro’s, and adding in other types of Nitro parrafins.

So what percentage do you try? For motors like Fox .35s, OS Max 35s or the old McCoy’s and K&B’s, use a fuel with 26 to 28% oil content; preferably half castor and half synthetic, up to 75% castor is OK. These motors have very small bearing surfaces, and are subject to much wear and heat, most are all plain bushing motors and most have unbushed rods. They need a lot of oil to help cool the engines. Since these motors run hot, they need extra oil to keep them lubed,clean, and to carry out heat . If you have one of these that is in very good shape but, is just starting to get some brown or black varnish plating on it, the synthetic mix will clean it up for you, resulting in increased life. Do not use the synthetic blend in an old motor that has a lot of time on it with all castor fuels; the synthetic will remove the castor varnish off the piston and sleeve and will in some cases, leave you with the worn-out motor that had to start with. Also always try to NOT use prop shaft extensions with these engine, as it adds a lot of wear on the crankshaft bearing.

For motors with larger bushings and bushed rods like to OS FP , Magnum GP series, Tower, and Brodak’s a 22-25% half-and-half oil mixture works the best. For S.T. .46 51,and .60s and most all ball bearings Stunt motors, a 23% half blend works best. Again the Synthetic blend will help keep the engine clean, and insure long life. If you use all castor in these types, it can stick the ring in the groove , resulting in poor compression and shortened engine life. If you have a ringed engine that castor has gummed up badly, most times running the synthetic blend will free the stuck ring, and the engine will return compression and power for you. The tuned pipe motors like a little more synthetic and I recommend a 15% synthetic, 7% castor blend or a 20% half and half with 1 ounce of Aero-1 fuel supplement. Although many use 1\2 – 1\2 with great success. This works very well in the Precision Aero , OPS and Max VF engines, Super Tigre Thunder Tiger, AERO TIGER and most all of these type engines..

Four Strokes engines also like the blend, I have found that a 15 % synthetic – 3% castor blend works well for them, normal oil percentage is 18 to 20 %. This will vary some from engine to engine, but is a good starting point. Most like 10 to 20 % nitro, going up to 25% to 30% in the hot summer weather. Aero-1 Fuel additive can help 4 strokes tremendously, as these engines are lubricated mostly by “blow by” and can run very hot. Fuel and tanks are also very critical for 4 stroke operation. Make sure you have a tank that delivers fuel easily to the engine, as four strokes don’t seem to like having to pull fuel from the tank. Use as short a fuel tank as possible and keep it close to the engine. A lot of people use muffler pressure or pumps to help feed the 4 stroke engines. I have used OS VF pumps, Perry vibration pumps and Perry pressure pumps with my test on 4 strokes. I would suggest,as we do with 2 strokes, to use a Sullivan “Crap trap” fuel filter. They hold a lot of junk ,and have a very good double cone design, that pushes the debris away to the sides and almost never stop up. If you get a stopped up filter on a four stroke ( or 2 stroke for that matter) you can burn the engine up in one flight

When you use motors for the first time, you should also make sure you have the motor properly broken in. This will range from six tanks of fuel for one engine to almost two gallons for others. OS, for example, says two hours running time for their motors. A good break-in procedure is to use the same fuel as you will for your Stunt run ,and try to do your break-in on a bench; this is a lot better and an easier way to do a proper break-in. A diameter, one inch smaller than you plan to run at, at a 3 or 4 pitch, should be the prop to use. This will let the motor turn many revolutions more per motor run time. Start out in a very sloppy four-cycle for cast iron lapped piston and most ringed motors, slowly progressing to the fastest it will run in a four-cycle, then put it in a short two-cycle burst for short times. After the correct amount of time it should be able to run in a two-cycle without heating up and going leaner. Using 3 to 6 ounces per run with 5 to 10 minutes cool down time in between.

For ABC, AAC ,ABL, ABC-R and ABN motors, start out in a very fast four-cycle and about every 45 seconds; pinch the fuel tube to kick the motor into a momentary two-cycle. These types of engines normally take more break-in time than do their iron lapped piston cousins . If you can run the motor in a fast four-cycle and without touching the needle, pinch the tubing to lean the motor into a two-cycle for 20 seconds or so, then it should go right back to a four. After breaking in the engine with a few tanks of fuel , you can start using the needle to cycle back and forth from 2 to 4 cycle. When it is broke in you should be able to hold a 2 cycle for 30 seconds or so, and come back to a 4 quickly by turning the needle richer . If not, it probably needs more running time.

Plugs can also be a major cause of trouble, and poor runs. When you first crank the plane, notice if it goes rich and sags slightly when the battery is removed; if so, the plug is normally too cold. This is critical to getting a proper Stunt run.

Most plugs are designed to provide a colder range than we want in C\L aerobatic engines , and you should try to get the right range for the motor. Many days of testing and much time and expense buying almost every plug on the market has yielded these results ;Thunder Bolt R\C long, T Bolt #3 , T Bolt 4 stroke, Glo Devil RC #300 long, Enya 3 & 4, Fireball RC long, the Hobby Shack RC long, SIC RC long a few of the OS hotter plugs and some of the FOX long and Miracle plugs are best plugs for our use. In almost all instances, use a long plus, as they will be substantially hotter than the shorts, plus they are deeper in the combustion chamber and this tends to keep things hotter and keeps the plug elements cleaner.

A lot of times the plug problems show up as rich inside maneuvers and leaner outsides; this happens because gravity and centrifugal force ,forces the oil-fuel charge down on the element on insides, thus cooling the coil and pulls it away on the outside maneuvers, letting it naturally go leaner. I have seen this problem instantly cured by simply changing plugs. Please do not be afraid to put in a new glo plug , or try different types of plugs . All of this assumes you have your tank height perfect (you did adjust your tank height, didn’t you), you’re right side up and inverted lap times are the same. This is important; don’t skip this step. If your using a profile sometimes you will need to have the tank center higher than the engine center. The 3 \16 to 3 \8 range will do for most fox 35s . Others will run on center line ,or just off of it. Another case of run problems are tanks or fuel delivery systems, which includes the tank, fuel tubing ,fuel filter, and anything else connected to the fuel system. When these problems arise in most cases, the engine changes speeds in flight, either faster or slower , and is generally inconsistent in the needle setting. This is almost always blamed as an “engine problem” when in fact it almost always turns out to be a tank problem, or fuel delivery system problem. I find most every time I see this , it is one component of the fuel system that is at fault. Either a hole in the fuel tubing, junk in the filter, a hole in the tank, a tank with an internal crack in the pick up or feed line . The next most common problem of this is water in the fuel. Water will give a very inconsistent needle setting, and will change at random back and forth from lean to rich. There are a few other things that cause problems with fuel delivery, muffler or pipe pressure will, most times magnify any little leak or problem you have and make things much worse than they were. A few other causes are an engine with a leaking backplate gasket, or an improperly cooled engine. A basic rule of thumb is to have a good intake area, with double the size of the exhaust area. Make sure you model (if fully cowled) has the air blowing all the way across and past the engine before the air flow exits the cowling. If your plane goes lean in maneuvers and comes back to a four-cycle slowly, it can be running too hot, you most likely need more oil, or less back pressure from the muffler. I have seen a lot of fuel with water in it (methanol attracts water) and this will cause erratic runs and needle settings. Always use fresh fuel and don’t be afraid to try another fuel if you think this is the problem.

Never try to put a brand new engine in a plane and try to break it in, trim and fly at the same time. I have seen this too many times with disastrous results. It is very hard to richen a too lean needle when the plane goes lean in flight. Keep good care of your equipment and it will usually take care of you; abuse it and it will most times let you down.

Now, a little more about fuels .For you guys who absolutely gotta buy the bargain R/C sport fuel…No amount of persuading will convince you otherwise; you at the very least need to add a healthy dose of castor oil. You can roughly figure 1.3 ounces will raise the oil content one percent (i.e. 13 ounces of oil to make 15% oil fuel into 25% oil fuel). This is not recommended and at the very best will usually be a guess, but it is much better than not adding anything at all, and I know people that do this all the time and get it to work for them .Example using Fire Power Cool 15%, pour off 13 ounces and add 13 ounces of Castor, this will be close to 11% nitro, and 24 to 25 % oil , this would make an OK fuel for plain bearing FP type motors, add a little more oil, and you have a fuel that you could run in your Foxes. The final thing I would like to say is to make sure you use an after-run oil between sessions and when you store the motors. This is another must do, because of the nature of the fuel we use. Then nitromethane or any nitropariffins burn, they leave behind, in your motor, acid and water, this, along with the water carried in partly by the alcohol, gets together and eats your bearing and other parts. Good quality after run oil is easy to get; don’t skip this step. If you can’t find a good after run at your local hobby shop, there are many available that are made by several companies…then try Prather’s. They make a good one and so does RJL and Aero Products. Do not use motor oil, Marvel Mystery oil; this is not after run oil.

Marvel makes excellent oil that can be used and as an after run oil and it is available from most auto parts stores and is called Marvel Air Tool oil. As a matter of fact, most air tool oils can be used as an after run oil; they are designed to fight corrosion in metal air tools and this is exactly what we are looking for. Another good place to get these types of oils are the large home supply stores like Home Depots and Builders Square type stores. Look in the department where they carry air compressor and paint guns. There are many brands of these oils so you see you have no excuse not to use them.

As for fuels, there are many good companies out there that will supply you with a good usable Stunt fuel. You will need to search them out in your area. . If you are using some of these suppliers, call them up. I’m sure most of them will oblige you. The model magazine are full of 800 numbers for fuel suppliers and the ones that I have mentioned come highly recommended; however, this is by no means all of them.

SIG for example has a very high quality fuel that is stocked by dealer all over the country; their Champion is 20% blended oil and with extra castor or oil supplements, such as AERO-1, makes an excellent Stunt fuel. Sig and I believe Power Master also make 20 or 25 % all castor fuels, as well as good 4 stroke fuel. Power Master is now making fuel for control line aerobatic planes, as are many other companies. There are more companies making good C\L stunt fuel such as S&W and others. I just don’t know them all and have not used their fuels in a while Keep in mind things will vary slightly, so don’t be afraid to try something new, or your buddy’s fuel if you suspect you have a fuel problem.

Randy..."Globee 4L plugs"..saw a batch of these sitting next to the water...Are they a plug one could use in the older Enya or S Tigre engines....I thought they used to be a racing plug and don't know if that necessarily means a hotter plug..or just a stronger element..Anyway..thought I would ask..

Thanks in advance...

HI Joe

Sorry I didn't see this post, The GloBee plugs have not been made in many many years, The 4L plug is a cold plug that is used in racing applications. The only GloBee plug we used that seemed to work well for Stunt was the GloBee4225 RC long or the 4225 GB2L

Randy , hello from a British ex-pat in the Charente region of France.Agree with all the other comments ....Really great article and priceless for us returnees to the sport.

May I just ask you to clear up an arguement between myself and colleages over on this side of the pond.

In your article you say it's fine to run the venerable Fox 35 on a 26%/28% mix of synthetic and castor.

My pals have told me: ONLY USE ALL CASTOR fuel.

Can I have your guidance on this ' sticky' issue please ?

Very much obliged ,

Robin.

p.s.Are the Evolution 36's in stock yet please ?

Hi Robin

The 36 Evo's are not in country yet , but will be soon.As the oil goes, I went into detail to explain why the synthetic-castor blend work better, I have FOX 35s I ran from the 1970s that have never been ran on all castor, and have 100s of flights on them,one has over 900 runs on it. They are in far better shape than any FOX 35 I have seen ran on only castor, and they still have tight front ends and the rods are not worn out, plus they are not coated with crusted burned on castor. 26 to 28 % oil is plenty enough for the FOX 35.The main reason people have worn out or broken FOX 35s with synthetic oil fuel, is they use a typical RC sport fuel that they bought from a Hobby Shop owner who told them it was "great fuel" and would work in anything, most of this has as little as 12 to 15% oil, even though they claim it is 18 to 20% oil. the lack of total oil was what killed the engine

The plug is a Thunderbolt R/C long No. 493115 and turning a B.E. 13 x 4.2 3-blader at 9'300 rpm, the motor runs in lean 4-cycle throughout the flight, beautifully adjusting power where needed. The pipe is a B.E. No. 8 set to 486 mm or 19.1 inches and I am using a Bru-line black mesh air filter on the factory std. venturi (0.189, I believe). Compression has been slightly reduced by adding a total of 0.008 in head shims. Consumption for 6:45 engine run time is 225 cc or 7.9 oz. (data for 1'400 ft/msl and 25°C)

So far, after approx. 100 flights, everything is just fine and the motor seems to be in perfect condition. However, after reading what you have published, I wonder whether I should increase the total oil content to 20 or 22%? Also, do you recommend that I use an after run oil?

Hello PeterIt is very good to hear from you, I hope this finds you well.I see nothing wrong with your setup. The fuel mix you are using will work fine in the engine running rich, You could up the oil to 20% and not hurt anything, however as loafing as the 75 runs it will work just fine on 18% oil content.I am personally using 19% oil mix 14% synthetic oil , 4% castor , 1% Aero-1 , for the 19% total on the 51 , 61, 65, and 75 PA engines.This blend helps the glo plugs last longer and runs very well in the PA motors.

A lot of times the plug problems show up as rich inside maneuvers and leaner outsides; this happens because gravity and centrifugal force ,forces the oil-fuel charge down on the element on insides, thus cooling the coil and pulls it away on the outside maneuvers, letting it naturally go leaner. I have seen this problem instantly cured by simply changing plugs. Please do not be afraid to put in a new glo plug , or try different types of plugs .

I don't understand. I would think the oil-fuel charge would get forced onto the plug element during the outsides maneuvers ??

Randy, would a bad plug also cause the motor to quit when it is too rich. That happened to me yesterday on my Ares, the motor was too rich and I did a shallow wingover and when I pulled out, the motor quit. we switched plugs and all was well after that

Randy, would a bad plug also cause the motor to quit when it is too rich. That happened to me yesterday on my Ares, the motor was too rich and I did a shallow wingover and when I pulled out, the motor quit. we switched plugs and all was well after that

Yes glow plugs will cause that.Matter of Fact many many "engine" problems are not at all, they are glow plug problems, either wrong selection or ones going bad. They can drive you crazy on inside vs outside manouver runs many times.if you start your motor and when you pull the plug, you get a drop in RPMs look at replacing the plug

I am behind the times and stuck in the 70s!Good times were had by all!

Getting into stunt after years in r/c and want to make sure I am headed down a good path on fuel.

When competing in C/L in late 60s early 70s fox fuel was my choice.40/40 for combat, Missile mist for slow ,super fuel for play. did not fly stunt back then.K&b for higher nitro contents in rat(synth?)Never any problems except when castor cost rocketed up and Fox tryed synthetics with disastrous results.

Have been R/C for recent history My newest engine is 25 year old ST small case .60 in R/C scale use.The fuel I have been running I think is going to be ok for fox .35, O.S. s.35 and st stunt .35 ,all are 1970s vintage.(after further thought not ok)

What I currently am using for r/cI have been using Morgan fuels Omega 10% with total oil of 17% with the oil being 30% castor and 70% synth.>To this I add 6oz of Sig Castor oil per gallon.<If I remember correctly several years ago My Dad calculated this to be around the 28% total oil mark by volume.This is from memory and I am learning not to trust it.(my memory)Basing it on your 1.3oz=1% I see it is only 21.6%

Possibly it was 2 6oz measuring cups full and the mind is playing tricks.This would give based on the 1.3oz=1%(12oz=9.23%) would be 26.30

Is this a workable stunt fuel for the older engines?I always try to stay on the fat side with needle settings.Its the accidental lean run with no way to shut it down that really worries me more than anything.

TerryI have personally taken 18% cool power and did a boil down test on it and got 14.6 percent oil total. I have also personally talked to people at Morgan and they told me that they do mix fuel by weight. this has been a while but I have seen no change in the fuel percentage , and I don't buy helicopter fuel to test in Stunt engines so that particular fuel may have more oil.

And No all companies do not measure by weight , several measure there mix by volume. Not that there is anything wrong with either way, But you do need to know if the fuel you have is made by weight or volume so you know what to use in what engine, and to know why the two run differantly, and to be able to get an accurate mix when adding oil or nitro to fuels for special applications...like getting low oil fuel to work in a FOX 35 without killing the engine

I have some other Morgan fuels, I will have to do a boil down on them.

My point was, you can mix by weight, but end up with the proper % by volume, if you correct for density.

Onlnie somewhere I did the calculations for mixing 5 gallons of fuel by weight, but end up with a given % by volume.

Hi Terry

And NO you can't mix by weight and come up with the right volume , If you tell people your fuel is 20% oil content and you measure by weight if most likley will be short of the people who mix by volume.And NO everyone doesn't measure by weight when mixing fuel, and there will be MORE nitro in fuel measured by volume...10% by weight will be less the 10% by volume, unless the oil is very thin 20% oil will be more oil when mixed by volume and LESS oil when mixed by weight.

Now if you want to calibrate what will give you 10% nitro and then mix that amount by weight, you can do that, same with oil, but always if the mixers blend fuel by weight you will get less nitro and less oil

You said""And this shows that if a company mixed TO % by weight, their fuel would perform significantly worse than other fuels due to the lower nitro content. And the higher the nitro content of the fuel, the greater the difference. 30% nitro, blended this way, would end up being 23.9% nitro, with 18.8% oil. ""

OK I will try one more time...

You are arguing with yourself, the point you are trying to make is MOOT and does not reflect what I stated. I am well aware that you can make blended by weight fuel..the same as by volume..but I have not seen any mfg. do that so far, except with a very small percentage of heli fuel. None of what you are saying has anything to do with the fact that fuel made by 20 oil by weight and 20% oil by volume are TWO differant percentages with the one mixed by weight having less oil....same with nitro

And that is exactly what happens with many of the companies, the fuel has LESS oil...........LESS nitro.......and performs LESS

That is WHY when I did a boil down test on 18% oil fuels it came out to be 14.7% !!! I don't understand why this is so hard to understand.It is OBVIOUS that some fuel companies blending by weight do NOT calculate the percentage to be the same as measured by volume.

It is also WHY the fuel does NOT perform as well as true % volume mixed fuel, When I make my own fuel measured by VOLUME , many many times the Hobby Shop fuel of the same Nitro percentage DOES NOT perform as well..it is DOWN on power and requires me to turn in the needle to get the same run and the by weight mixed fuels run much longer...with LESS power.

I have also take SIG 10% nitro 18% oil fuel and ran it against Brand X fuel of the same and the SIG fuel ran shorter time with more power and had a better run and a better needle, the Brand X fuel was down on power, short of oil, and ran much longer.

""The proper question is ask is, "Do you mix to % by volume or % by weight?" Asking just, "Do you mix by volume or by weight," may get you a technically correct answer, but NOT tell you what you want to know.""

When you talk with the chemist of a fuel company who is in charge of the mixing and he tells you that their fuel is 18% oil....the you do a BOIL DOWN test and you get 14.7% the question is answered ...period!

How do you safely do the "boil down" test to check for oil content in unknown fuel? Thanks!

Paul Gibeault

I use 100ML beaker with a hot plate outside, put it into a pot of boiling water about 2 to 3 inches deep, add water as needed to the pot, NOT to the beaker, then after you have it boiled away stir it while hot to make sure, then remover the beaker and read what is left, do the math and presto you have you %

others have used a heat gun outside with the Pyrex beaker to boil off the fuel, do NOT use an open flame!

I'm using a LHS 15% fuel (one gal) to which I've added 4oz of castor oil. Does that sound OK?

Many thanks in advance.

Andy

Short reach glowplugs for .15 and smaller, Long reach for bigger than .15. All of those will be happiest with a good hot glowplug. There are several good brands available, most of which are actually made by Ohlsson Corporation. That probably sounds familiar...O&R or Ohlsson & Rice. I like Thunderbolts a lot...R/C Long idle bar or 4-cycle works for me and most everybody I know. K&B, RO-Jett and Zinger also...and also made by Ohlsson. Can't say about SIG. Some guys like Fireball, but get the red (hot) if you try them. Merlin glowplugs have a good reputation, as do OS and Enya. I'm not a fan of Fox glowplugs at all.

If the fuel is locally brewed, I'd ask 1) what % oil 2) what oil and 3) how the components are measured, volume or weight. Most R/C fuels really need more like 8 oz of castor added to be safe for old tech engines!!! Steve

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Short reach glowplugs for .15 and smaller, Long reach for bigger than .15. All of those will be happiest with a good hot glowplug.

Thanks, Steve

I'm using these old engines on u-control models. Because of their age and this use, do I need plugs with the idler bar? I am not at all familiar with the idler bar concept. Seems like a lot has changed over the years!!

I have a fuel tank question...mostly because I'm still back in the Perfect metal wedge days and am amazed at all the types on the market today.

What is best for sport/stunt control line flying?

Andy

A leak free tank that provides the desired run. There is no best answer, other than a leaky or incorrectly plumbed tank will be a nightmare.

I am setting up with plastic tanks, plumbed with a clunk and a fixed uniflow vent on exhaust pressure. I will have a fueling disadvantage since I need to have the airplane up on the wingtip to fuel through the feed line. These are flite streaks so no big deal on the position, but I would plumb a separate vent on anything bigger.

I gave up on metal tanks (other than bee tanks) for 1/2a when I started flying again a couple years ago. I use bladder, either pressure or non-pressure, depending on the engine setup.

I am setting up with plastic tanks, plumbed with a clunk and a fixed uniflow vent on exhaust pressure. I will have a fueling disadvantage since I need to have the airplane up on the wingtip to fuel through the feed line. These are flite streaks so no big deal on the position, but I would plumb a separate vent on anything bigger.

I gave up on metal tanks (other than bee tanks) for 1/2a when I started flying again a couple years ago. I use bladder, either pressure or non-pressure, depending on the engine setup.

Phil

Phil

I don't understand what you mean in the parts that I have put in bold. Can you add a little more to that?

Bladder is a flexible fuel tank made out of some type of fuel resistant material like latex. I think it was made popular with combat since it prevents air from being in the system and allows for reliable engine runs as a result.

Non-pressure bladders would be latex party balloons, a common 9 inch balloon can be set up so it can hold from about 1 oz to over 2 oz. The air is removed using a fuel syringe and then the measured amount of fuel is put in. It functions via suction. The idea is to always have a relaxed balloon.http://stunthanger.com/smf/index.php/topic,38539.0.html

Bladder is a flexible fuel tank made out of some type of fuel resistant material like latex. I think it was made popular with combat since it prevents air from being in the system and allows for reliable engine runs as a result.

Non-pressure bladders would be latex party balloons, a common 9 inch balloon can be set up so it can hold from about 1 oz to over 2 oz. The air is removed using a fuel syringe and then the measured amount of fuel is put in. It functions via suction. The idea is to always have a relaxed balloon.http://stunthanger.com/smf/index.php/topic,38539.0.html

Thanks much for taking the time to help me with this...I have to admit it will take a bit to absorb that info. I guess I'm stuck on the old Perfect metal tank idea with its three tubes...not too sure this old dog is ready for new tricks!!

Thanks much for taking the time to help me with this...I have to admit it will take a bit to absorb that info. I guess I'm stuck on the old Perfect metal tank idea with its three tubes...not too sure this old dog is ready for new tricks!!

Andy

If it is a good tank without leaks those can work pretty well. The key is that they need to have no leaks. I have an old perfect tank in my super ringmaster, and after getting it cleaned out inside performs quite nicely with the Fox 35 on it.

If it is a good tank without leaks those can work pretty well. The key is that they need to have no leaks. I have an old perfect tank in my super ringmaster, and after getting it cleaned out inside performs quite nicely with the Fox 35 on it.

Phil

Good point!

I'm sure my old tanks have unwanted goop inside...what do you use to clean them out?

I filled the tank with denatured alcohol... I had to use some wire to poke through the gunk to do this, then threw the tank in a jar full of denatured alcohol. A week or so later I forcefully flushed the loose debris out with both air and more denatured alcohol using a large fuel syringe. I then pressure tested using the fuel syringe in a sink of water.

I filled the tank with denatured alcohol... I had to use some wire to poke through the gunk to do this, then threw the tank in a jar full of denatured alcohol. A week or so later I forcefully flushed the loose debris out with both air and more denatured alcohol using a large fuel syringe. I then pressure tested using the fuel syringe in a sink of water.

Phil

Sounds good. I'll give that a go and see what comes out after 50 years or so!!

I have been going over the posts again to understand the oil mix issue when running old engines.

I ran my Torpedo 23 the other day on a stand and it smoked a bit after shut down...and it seemed to me that the green color of the head had darkened up a bit. Obviously something was hotter than it should be.

I am using Omega 15% to which I added 4 oz castor without reducing the quantity of fuel in the container. I now think I didn't read these posts carefully enough.

The Omega specs say this fuel has 17% lubrication. Using Randy's 26-28% numbers and estimates, it seems I needed to add about 13oz of castor after removing 13oz of fuel first.

Is that correct?

I really appreciate the help...I don't want to damage engines I've had from when I was a kid.

The link says that the additional oil is added to the existing gallon...I may have also read where the 18oz of oil would be added after 18oz of fuel was removed. Did I misunderstand?

Thanks much for the link.

Andy

No you have it, remove the fuel and add the extra oil, then shake well, save the fuel in a qt jar, and you will be OK adding15 ounces of oil, you won;'t need 18 ounces. This will cut your nitro percentage, so use a step higher nitro, ie.. if you want 10% start with 15%, if you want 5% start with 10%.. remember the nitro is also lower , because most of these type fuels are measured by weight and NOT volume.

No you have it, remove the fuel and add the extra oil, then shake well, save the fuel in a qt jar, and you will be OK adding15 ounces of oil, you won;'t need 18 ounces. This will cut your nitro percentage, so use a step higher nitro, ie.. if you want 10% start with 15%, if you want 5% start with 10%.. remember the nitro is also lower , because most of these type fuels are measured by weight and NOT volume.

A most helpful and indepth post! You explained many things that I learned the hard way, some of which I had forgotten after 30 years away, and you explained the details of some things that I knew were the case, just didn't know exactly why. Not to mention things I just didn't know at all. When I got back into the sport last year my old Fox 35 Stunt simply refused to run right on the new fuel I bought. It was 5% nitro and 50/50 synthetic/castor totaling 18% oil. After discussing this with a much more experienced flyer I was told that the Fox engines like this need more like 28-30% oil. I added castor until it should be about 30% and it runs great. This also seems to work ok, so far, in my Thunder Tiger 46. Though this plane has only 2 flights on it with no stunt work yet.

Its plain to me that as my building and flying continue I will need to stock various fuels for different uses. Thanks again for a most informative article!

Just stumbled onto this thread and so glad I did! I've been away from control line for a long time, (35+ years) and I have been lurking on the forum for a while trying soak up all the info I can. I just want to thank you guys for being so helpful with threads like this one with so much good information!